Polychloroprene thiotriazine acceleration



United dtates Patent 0,

POLYCHLOROPRENE THIOTRIAZINE ACCELERATION Ralph A. Naylor, Stamford, Conn., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application February 26, 1954, Serial No. 412,953

8 Claims. (Cl. 260-923) strength, percent elongation, the breaking point or aging characteristics.

In general, accelerators for rubber were of little or no value in curing synthetic rubbers known as polymerized chloroprene.

. According to this invention, these diificulties are surprisingly and effectively overcome by adding to a formulation of chloroprene rubber a thio-substituted symmetrical triazine vulcanization accelerator characterized by the formula:

wherein R is mercapto or amino and R1 is mercapto, 2- mercaptoarylthiazylamino, amino, arylamino, alkylamino, dialkylamino, cycloalkylamino, or N-alkyl-N- arylamino.

Among the substituted triazines I may use are: thioammeline, dithioammelide, trithiocyanuric acid, N-methyl- N-phenyl dithioammelide, N- phenyl dithioammelide, N- dibutyl dithioammelide, N-cyclohexyl dithioammelide and N-(Z-thiobenzothiazyl) dithioammelide.

It has been further found that by increasing the tbiol substituent from one to three, the activity with respect to tensile strength and modulus is rapidly improved. However, maximum activity is obtained with a di-N-substituted dithioammelide.

A synthetic chloroprene rubber made by polymerizing Z-chlorobutadiene 1,3 (known as neoprene) may be vulcanized or cured by adding the designated accelerator to an unvulcanized composition. Alternatively, the accelerator may be added to a partially cured neoprene polymer. As a preferred embodiment of the invention, it is preferred to accelerate the vulcanization of Neoprene Type W. The latter neoprene is a nonsulfur-modified rubber made by the emulsion polymerization of chloroprene (2-chlorobutadiene 1,3) and which is devoid of sulfur, thiuram disulfide or other compounds capable of 7 2,804,450 Patented Aug. 27, 1957 decomposing to provide either free sulfur or a vulcanization accelerator.

The amount of accelerator added to the rubber composition may vary from 0.25 to 2.5 parts of accelerator per 100 parts of polymer. However, for most purposes,

the range may vary from 0.5-1.5 parts of accelerator per parts of polymer.

Temperatures which can be employed to cure neoprene polymer compositions may vary from about C. to 200 C. depending on the time of cure and amount of accelerator added. In general, adding larger amounts of accelerator to the composition and employing a longer curing time, the temperature should proportionately be reduced. It has been found that for the customary time of cure and accelerator addition, the temperature of curing may vary from about C. and C. For excellent results, a temperature of 153 C. is employed.

In the following example a typical stock formulation is illustrated with and without a vulcanization assistant. However, these examples are presented by way of illustration and not by way of limitation. The parts as designated in these examples are by weight.

Example 1 A batch mixture comprising the following:

Neoprene Type W 100 Phenyl alpha naphthylamine 2 Stearic acid 0.5 Light calcined magnesia 2 Semi reinforcing furnace black 29 Zinc oxide 5 Thioammeline 0.5

is heated at 153 C. for 10, 20'and 40 minutes respectively.

Example 2 Example 1 is repeated with the omission of an accelerator.

Example3 Example 1 is repeated except dithioammelide is substituted for the thioammeline vulcanization accelerator.

Example 4 Following the procedure of Example 1, trithiocyanuric acid is substituted for the vulcanization assistant therein.

Example 5 N-rnethyl-N-phenyl-dithioammelide replaces the accelerator of Example 1. The procedure of that example is then repeated.

Example 6 Following the procedure of Example 1, N-phenyl dithioammelide is substituted for the vulcanization assistant therein.

Example 7 Example 1 is repeated, except N-(Z-thiobenzothiazyl) dithioammelide replaces the accelerator therein.

The characteristics of the neoprene thus vulcanized in the foregoing examples are tabularized below.

M minutes at 163 C. minutes at 153 C. minutes at 153 C.

ooney Example Accelerator Scorch 1 Modulus Tensile Percent Modulus Tensile Percent Modulus Tensile Percent at 300% Elong. at 300% Elong. at 300% Elong.

1 Thioammellne over 30 150 1, 025 1, 125 600 2, 625 800 625 2, 825 800 2 None over 600 900 500 2, 575 800 575 2, 700 780 3 Dithioammelide- 43 .250 ,1, 650 940 675 3, 780 700 2, 925 720 'Iritliiocyanurieaeid 12 675 '2, 750 760 875 3, 200 700 1, 200 3, 225 590 N metll yile N phenyl dithio- 112' 1; 1253 ..3, 275 620 1, 3, 425 630 1,175 3, 250 590 .amme l Y "450 2, 400 820 700 3, 000 700 775 3, 250 720 125 r 975 1,050 475 2,475 1820: 1550 2675 800 v 225 1, 425 100 600 2, 775 7,60 825 3,100 720 I50 '1, 100 1, 550 2,750 810' 775 3, 225 740 *amm'elide.

r -l;Mooney-scorch'time in ,minutes-ioriaten; pointrlse above the minimum reading using the small rotor at 250 F.

Modulusand tensile strength in p. s.

;It.-can-be readilyseen.from itheaabovetable that bylinwreasing .the thi ol substituents, the vulcanizate charac- -teristicsare rapidlyimproved. Further, the best improve- .mentsis obtained 'Withnfldi N2SDbStit-llt6d dithioammelide accelerator.

The vulcanizedrubbenmadein accordance with this invention is useful-for services wherein-improved strength is desirable in addition to the normally-good oil and heat resistance of 'the polymer, rforexample, as gasoline filling hoses or motor mountings.

.Suitable variations andchanges-imthe invention maybe made without departing :from the :spirit thereof or the scope of the appended claims.

I claim:

1. A process for improving the modulus, tensile strength and-elongation :of chloroprenetrubber compositions comprising adding to an unvulcanized vulcanizable gchloroprene rubber composition between 0.25% and 2.5% *of asymmetrical substituted thiotriazine, and curing said composition at vulcanization temperatures.

7 2. A process for improving the modulus, tensile strength and'elongation of chloroprene rubber compositions comprising adding to an unvulcanized vulcanizable chloroprene rubber composition" between 0.25% and 2.5% \of asymmetrical thiotriazineiaccelerator characterized by the formula: N

wherein .R is the radical selected :from the .-group consisting of mercapto and amino-and R1 -is the radical selected from the group consisting of mercapto, 2-mercaptoarylthiazyl amino, amino, alkylamino, arylamino, dialkylamino, cycloalkylamino and N-alkyl N-aryl amino, and curing: said composition-at :vulcanization temperatures.

3. The; process according toclaim 2.wherein the chloroprene .rubber is a rnonsulfuramodified chloroprene polymer.

'4. The process according to claim 1 wherein the accelerator is dithioammelide.

$5. The process according to claim 1 Whereimthe accelerator :is trithiocyanuric -.acid.

'6. ;A process according to :claim 1 wherein the ac- .celerator .is rN-methylr-N-phenyl'rdithioammelide.

7. .A process according .to claim 1 wherein'the acceleratoris rNephenyl dithioammelide.

8. The-,process .according toclaim 1 wherein tho accelerator is dibutyl dithioammelide.

References .Cited;in the filegof this ,-patent UNITED STATES PATENTS .Baum Mar. 13, 1951 

1. A PROCESS FOR IMPROVING THE MODULUS, TENSILE STRENGTH AND ELONGATION OF CHLOROPRENE RUBBER COMPOSITIONS COMPRISING ADDING TO AN UNVULCANIZED VULCANIZABLE CHLOROPRENE RUBBER COMPOSITION BETWEEN 0.25% AND 2.5% OF SYMMETRICAL SUBSTITUTED THIOTRIAZINE, AND CURING SAID COMPOSITION AT VULCANIZATION TEMPERATURE. 